A device includes a housing, an emitter, a detector, and a processor. The housing has a body contact surface. The emitter is coupled to the housing and has an emission surface and has an electrical terminal. The emission surface is configured to emit light proximate the body contact surface in response to a signal applied to the electrical terminal. The detector is coupled to the housing. The detector has a sense surface and an output terminal. The detector is configured to provide an output signal on the output terminal in response to light detected at the sensor surface. The processor is configured to implement an algorithm to determine a tissue site based on the emitted light and based on the detected light.
